*{margin:0;padding:0}
ul{
    overflow:hidden;
    list-style:none
}
ul li{
    width:50px;
    height:20px;
    background:green;
    float:left;
    margin-right: 5px;
}
ul li.action{
    background:red
}
div img{
    width:500px;
    height:200px;
    display:none
}
div img.action{
    display: block
}